The 5% nitro will get better fuel mileage than 15% and that is a proven fact. It is reported that the Fox Idle bar plug gives the right timing to any Super Tigre engine. I can't say different since I use the RClong in every Tigre I own from 40-1.80 (3000) except for my 4 strokes (non ST's of course). And 1 Tiger shark 61 that needs a KB1L And Like I said the 15% is about double in your country............